Anything with a temporal "half-life" or finite storage capability: e.g. Experiences, Moments, Sensations, Memories
Or how about Breaths? - if you stop making them, you certainly don't leave any more behind.
blackjack
<a href="http://c.casalemedia.com/c?s=51816&f=3&id=0" target="_blank"><img src="http://as.casalemedia.com/s?s=51816&u=http://perplexus.info&f=3&id=0&if=0" width="120" height="600" border="0"></a>
flooble's webmaster puzzle
more
